Farmers risk irrigating crops with sewage

With food shortages threatening billions of people around the world with starvation, millions of acres of agricultural land in developing countries is being watered using wastewater and sewage.

A 53 city study by the International Water Management Institute (IWMI) found that 85% of water is discharged from cities without appropriate treatment, often to be reused on agricultural land.

In more than 70% of the cities surveyed, over half of the agricultural land is watered using raw untreated sewage, or sewage watered down in streams.

This presents a major health risk for those tending the crops, as well as to those that eat the crops.

Despite the health risks, irrigating crops with wastewater has a number of benefits, including allowing food to be produced where clean water is in short supply, recycling nutrients, and treating the water that would otherwise cause health problems downstream.

Ideally, wastewater should be partially treated before it is used on crops to prevent health risks whilst maximising its benefits.

Simple treatments include keeping the water in a pond before it is used to allow solids - including the eggs of worms - to settle.

Crops should be washed with clean water once they are harvested, a luxury which all too many people are unable to afford.